In a wireless communication system, Hybrid Automatic Repeat Request (HARQ) ACK/NACK information indicating whether data transmitted from a transmitter has been successfully decoded by a receiver can be transmitted from a receiver from the transmitter. For example, an error detection code (for example, cyclic redundancy check (CRC)) may be added to data transmitted from the transmitter in units of a codeword, such that the receiver may generate ACK/NACK information in units of a codeword. For example, information as to whether one codeword is successfully decoded may be represented by ACK/NACK information of 1 bit.